1. Field of the Invention
The present invention relates to a camera which comprises a finder device for controlling a finder on the basis of the visual axis information of an operator.
2. Description of the Related Art
Conventionally, when an operator inputs various kinds of information to a camera, he or she attains this operation by operating a corresponding dial, button, or the like. Therefore, as the number of pieces of information to be input increases, the operation environment becomes more complicated for an operator.
In consideration of this problem, a large number of techniques for detecting, e.g., the visual axis direction of an operator who looks into a finder, and inputting various kinds of information to a camera on the basis of the information of the visual axis direction are disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication Nos. 63-194237, 3-87818, and the like.
As for the visual axis detection methods, a large number of techniques for detecting the visual axis direction of an operator using light reflected by at least one of the cornea, iris, pupil, sclera (the white of the eye), and the like of the operator's eye are disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2-206425, and the like. Furthermore, a large number of techniques for determining distance measurement information on the basis of the detected visual axis position are disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 4-307506, 5-88075, and the like.
In signal processing of a sensor as well, differential processing of signals in ON and OFF states is often performed in synchronism with operation of a light projection LED. For example, Jpn. Pat. Appln. KOKAI Publication No. 2-138673 discloses a method of performing pupil detection by performing differential processing of signals obtained based on light beams projected from different positions, i.e., a red-eye position and a non-red-eye position.
On the other hand, in a diopter adjustment technique, a technique for changing the diopter state in correspondence with distance measurement information is known to those who are skilled in the art. Furthermore, a technique associated with a camera for detecting and correcting the imaging state of an eye is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 63-206731. As a method of detecting the imaging state of an eye, a method of observing the retina on the fundus of the eye is disclosed in the magazine, "O plus E., No. 115, Jun, 1989, pp. 123-125, Physiological Optics, 2nd Volume". As one of objective methods for detecting the imaging state of an eye on the basis of the state of fundus light, the skiascopy is known, in which a feature is produced in a red-eye phenomenon of reflected light depending on the light source position for projecting light.
Compact cameras popularly adopt real-image finders. Therefore, when the objective optical system and the eyepiece optical system are not in an in-focus state, an in-focus image cannot be obtained. More specifically, in the real-image finder, since the imaging position is fixed, if the observation position of an operator is other than a setting position, the operator observes an object by using his or her focus adjustment faculty. Therefore, when the focus adjustment faculty of the operator's eye is low, the operator observes an object in an out-of-focus state, i.e., an out-of-focus image.
Furthermore, diopter adjustment is normally attained by driving an optical system to a setting position with reference to a predetermined display in a finder. However, in the real-image finder, an object image is often imaged at a position other than the setting position depending on its distance. When, especially, an objective optical system in a finder optical system is driven to correct the imaging position to be an optimal setting position, an operator can no longer follow the change in frame, and cannot comfortably use the camera.
Furthermore, in the case of a finder of a camera, both near and far objects are often present, and even when some correction is performed based on distance measurement information, the observation portion of an operator does not always match the corrected position.
In order to solve these problems, a technique for adjusting the diopter by moving, especially, the objective optical system in the finder optical system on the basis of distance measurement information has been studied. In this technique, the observation state in the finder can be further improved if the visual axis direction of an operator is detected.
Note that the techniques associated with a visual axis detection system have already been put into practical applications such as in selection of distance measurement information. Furthermore, the techniques for improving the observation state in the finder by changing the diopter by moving a portion of the finder optical system have already been put into practical applications. In addition, in association with a plain finder, i.e., a real-image finder, the technique for driving a portion of the finder optical system on the basis of diopter information has been studied. However, since objects with different distances are often recognized simultaneously in the finder, if a portion of the finder optical system is driven based on specific distance measurement information, an object which an operator wants to observe may become out of focus.
Since an operator observes an object image via the finder optical system and an optical system which can adjust the focusing state of the eye, if a portion of only the finder optical system side is driven to an optimal position on the basis of distance measurement information obtained by measuring the object distance, the operator's focus adjustment faculty cannot follow this movement, resulting in an unnatural finder image.
Furthermore, upon driving the optical system, the in-focus position fluctuates around the optimal position, and a finder image becomes more unnatural.